usb: cdns3: introduce set_phy_power_on{off} APIs

Since we have both USB2 and USB3 PHYs for cdns3 controller, it is
better we have unity APIs to handle both USB2 and USB3's power, it
could simplify code for error handling and further power management
implementation.

Reviewed-by: Pawel Laszczak <pawell@cadence.com>
Reviewed-by: Jun Li <jun.li@nxp.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>